1. Technical Field
The present invention relates generally to integrated circuits implemented in image sensors and, more specifically, to a voltage regulator circuit having a distributed output network.
2. Introduction
Conventional image sensor technology typically implements a standalone voltage regulator to supply power to pixel arrays and readout circuitry. However, for image sensors having large pixel arrays, voltage variation is prevalent along the columns or rows of pixels due to IR drop (voltage drop) across a metal output track of the regulator. The IR drop across the output track results in unequal source impedances at each of the pixel columns or rows in the pixel array, causing various problems such as, for example, droop and unequal settling time for each pixel column or row. What's more, conventional voltage regulator circuits typically implement a dense unit transistor layout that often generates large amounts of heat within the circuit during high current consumption. As such, conventional regulator circuits suffer from heat dissipation issues that result in degraded performance and reduced lifespan of the device.
One solution for addressing the IR drop is to increase the width of the metal output track connecting the columns or rows of pixels. However, this solution requires a significant amount of circuit space, which is further complicated by the fact that the image sensor is only able to dedicate a limited number of metal layers for routing. In cases requiring high current consumption, any efficiency provided by this solution is generally minimized for applications incorporating a large pixel array. In addition to requiring significant space in the circuit, the greater track width may jeopardize stability of the regulator by causing an increased load capacitance. This proposed solution also fails to address the heat dissipation issues. Therefore, there exists a need for a voltage regulator circuit that reduces IR drop and improves heat dissipation without requiring a significant amount of additional circuitry within the regulator circuit.